This invention relates to pumps, and in particular to piston type pumps for pumping liquids to significantly higher elevations and pumps having energy recovery means.
Pumping liquids against substantial hydraulic heads is a problem encountered in pumping out mines, deep wells, and similar applications such as pumping water back up, over a hydro dam during low energy usage periods, for subsequent recovery during high energy usage periods, and for use in run-of-the-river hydro power applications utilizing the potential energy of water in a standing column.
A number of earlier patents attempt to provide devices which utilize a piston type pump where energy is recovered from a column of liquid acting downwardly on the piston, as the piston moves downwardly, in order to assist in subsequently raising the piston together with a volume of liquid to be pumped upwardly. An example of such an earlier patent is U.S. Pat. No. 6,193,476 to Sweeney. However such earlier devices have not been efficient enough to justify their commercial usage. For example, in the Sweeney patent, the efficiency of the apparatus is significantly reduced due to the fact that the upper piston 38 has the same cross-sectional area as lower piston 43. Thus the pressure of liquid acting upwardly on the lower piston 43 inhibits downward movement of the upper piston 38 under the weight of the liquid in the cylinder above.
It is an object to the invention to provide an improved pumping apparatus capable of pumping liquids against significant hydraulic heads, such as encountered in deep wells or in pumping out mines, without requiring pumps with high output heads.
It is a further object of the invention to provide an improved piston type pumping apparatus with provision for energy recovery, having significantly improved efficiency compared with prior art devices of the general type as well as the ability to use the potential energy of a standing column.
It is still further object of the invention to provide an improved piston type pumping apparatus which is simple and rugged in construction, and efficient to operate and install.